The polyurethanes are polymers usually prepared by the condensation reaction of diisocyanates or polyisocyanates with polyols. Their area of application is extremely vast because of the fact of structural and textural differences which it is possible to obtain, permitting a large range of products ranging from flexible foams to rigid elastomers. The standard synthesis of isocyanates starting from hydrocarbon structures, cells upon three reaction stages, namely, nitration, hydrogenation and phosgenation.
This necessitates having at one's disposal different equipment for each stage, purifying generally by distillation the diamine and then the diisocyanate, synthesizing and manipulating the phosgene, a dangerous product, which furthermore involves the co-production of hydrochloric acid which must either be used in other reactions or be electrolyzed in order to recover the chlorine and the hydrogen. Hence, there is also the costly upkeep of an electrolysis shop.